Can you identify this diff?

Can anyone identify this diff?

Look at the nasty weld in this one, yet the other end bolts appear to be different.
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How was the condition of the bearing and the seal? Were the bearings leaking? What do you think of this possible scenario. Maybe the bearings and seal are wearing from age, loosing lubrication, then binding/wearing creating bearing play which then transfers to the diff creating stress from movement in the bearing, then something gives way (diff weld). Just something I was thinking about. Any input or opinions are greatly appreciated.

R

 

Isn't an uncracked weld a good weld?

"...yet the other end bolts appear to be different." -- different from other bolts in the same assembly, or bolts in other diffs, or ? Any chance that you can post a clearer picture of the head markings in question?

 

I'm sure this has been asked many times before but can the diff be changed without an engine out?

 

Yes mine was. Not an easy job though.

 

They are, until they're not.

Glad we have some better<coughBILLETcough> options now.

 

It looks like the weld was machined for clearance. I don't think you can tell much about the weld by looking. Something else is going on like not being stress relieved or something else.





Ago

 

Depends on the grade. If it's 304 which is very common, it has excellent machinability and weldability but cannot be heat treated. It's also a relativity expensive grade but that is negligible in this application.

http://www.azom.com/article.aspx?ArticleID=965

There are not many materials that have all the properties a diff casing requires.

Machinability
Corrosive resistance
Hardness
Weldability
Yield strength

I've had better luck with the 400 series, especially a modified 430F (low Sulfur). Machines and welds great. 410's are also easy to heat treat and machine relatively well.

http://www.azom.com/article.aspx?ArticleID=996
http://www.azom.com/article.aspx?ArticleID=970

 

Why use stainless steel? I would of guessed 4340. Then normalized after welding.


Ago

 

The diff came out of a 512BBi with 4500 miles on the clock.

To my eye it doesn't appear to be the factory diff so I'm wondering if any of you guys have seen a diff that looks like this or can you compare it to your own 512's?

 

Hi Rob, did you compare it with a "newer" TR one ?

In fact anybody can make a diff housing if appropriate measurement was done ...

I would not place that diff back, that's for shure ...

How did you come by this one if I may ask ... ?

 

Belongs to a friend of mine who has had it removed from his car.

He's pretty sure the mileage on his car is accurate at 4500 UK Miles but this diff doesn't look to be standard in a 512BBi, so I'm asking if any of you guys have seen one like it before.

 

Rob,
That diff looks pretty much the same as the one I pulled from my car. The circle cutout in the diff housing is like the original diffs up to the M diff which had a square cutout. The small bolt heads look correct and the welded seam area is machined after welding to ensure it does not interfere with the diff housing.

 

Photos show 1990 Testa diff with out crown and bolts/tabs. looks very similar with a slightly tidier weld.
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" The circle cutout in the diff housing is like the original diffs up to the M diff which had a square cutout. "

You mean this (not welded) oem version Mike ... it is late 1994.

If you look at the remains of my 1992 512TR diff the welds were actually pritty nice and flat/smooth ..... but what if the don't hold ...

I showed it all to 2 TR drivers ... explaining what may also be coming to them in future .... they were deeply impressed ...
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Yes Mel the top one in your photo is the M diff and my reference to square cutout was incorrect as it is at the weld end and not the bolt head end where I think it is still a round cutout. Thanks for the pictures Mel.

 

THIS top one now is ....> the OEM later 512TR version, produced since 1992 ! And of course also of the 512M ....
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Mel,
How thick is the metal where the weld broke? I would surmise that this was an automatic weld. Maybe there wasn't enough weld penetration and they machined away too much for clearance. It could be that there was changes in the weld procedure and they didn't address it correctly.


Ago

 

It an original diff, the welds vary from unit to unit and tend to get lighter with the new cars as power and weight go up.

 

Thanks Paul.

 

IMO....the bearing is spinning on the snout to which it has a press fittment...the shoulder under the bearing CLEARLY shows-along whith obvious and visible rotational stryations on the snub axle itself-indicates to me that the bearing was "spinning on the snub", which causes things, and will result in....HEAT, and slop within the preload and side cover shim clearance spec numbers, ALL resulting in a "hammering" of the dome with the oft spoken weld, as each time the driveline is loaded(each time you release the clutch for example), the "hammering" combined with the heat generated from spinning, will weaken ANY weld in an environment as hostile as the one LSD resides.....
IMO....it looks JUST like aq worn out-but un fractured-365GTB/4 LSD snout, althought the peculiarities of that repair are slightly different-the cover-that here, but indicators are remarkably similar....remarkably....